Transferring heat by radiation between a thermometer and its surroundings can lead to errors in measuring temperature, especially when the temperature of a gas is measured by a thermometer positioned near surfaces at higher or lower temperature than that of the gas. This measuring error is also affected by other factors such as
the velocity of the gas crossing the thermometer, the physical size of the thermometer and the emissivity of the same thermometer. A set of thermocouples is used in this equipment to measure the temperature of the air flow crossing the centre of a duct while the side walls of the duct are heated, so that thermocouples are supplied with a source of heat radiation. Each thermocouple receives heat by radiation from the heated surface and loses heat by convection to the air and along the wires, by conduction. The result is an increase of temperature of thermocouple above the temperature of the air and consequently a reading error of the same thermocouple. This equipment enables to show these sources of error in measurement besides supplying suitable methods for reducing or eliminating these errors.
TRAINING PROGRAM
This unit enables to develop and analyze the following issues:
• Errors concerning radiation heat transfer:
– effect of wall temperature
– effect of air velocity
– effect of thermocouple type
• Methods for reducing errors due to radiation
TECHNICAL CHARACTERISTICS:
• Tubular duct of stainless steel with a wall heated electrically at 200 W @ 24 Vdc
• Electric fan
• Three K-type thermocouples (d= 1.6 mm, d= 1.6 mm, black painted, d= 4.8 mm)
• Air lock for varying air velocity
• Anemometer, range 0-10 m/S
• Movable shield against radiation
